Mesoscale Discussion 1921

Issued

Aug 9, 2011, 5:02 PM MDT (23:02 UTC)

Expired

Aug 9, 2011, 7:00 PM MDT

In force

118 min

Issued by

the Storm Prediction Center

The Cheyenne radar (KCYS), 150 km from the middle of the area, began a volume at 23:03 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Severe Thunderstorm Watch 759Aug 9, 5:55 PM MDT
• Severe Thunderstorm Watch 760Aug 9, 8:50 PM MDT

012 
ACUS11 KWNS 092302
SWOMCD
SPC MCD 092302 
KSZ000-NEZ000-COZ000-SDZ000-WYZ000-100100-

MESOSCALE DISCUSSION 1921
NWS STORM PREDICTION CENTER NORMAN OK
0602 PM CDT TUE AUG 09 2011

AREAS AFFECTED...PORTIONS WRN NEB...WRN KS...NERN CO...ERN
WY...EXTREME SWRN SD.

CONCERNING...TORNADO WATCH 754...

VALID 092302Z - 100100Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 754 CONTINUES.

CONTINUE WW.  WHILE TORNADO THREAT HAS DIMINISHED...SVR POTENTIAL
STILL APPEARS RATHER WIDELY DISTRIBUTED...IF ISOLATED TO WIDELY
SCATTERED IN COVERAGE...ACROSS WW.

SFC MESOANALYSIS SHOWS COLD FRONT FROM CENTRAL MO WNWWD ACROSS
SLN-RSL-HLC AREAS...DECELERATING WITH WWD EXTENT.  PREFRONTAL
CONFLUENCE LINE WAS ANALYZED NEAR HLC-EWK-CNU...DRIFTING SEWD OVER
ERN KS AND QUASISTATIONARY ELSEWHERE.  ANOTHER WAVY CONFLUENCE LINE
IN WARM SECTOR WAS DRAWN BETWEEN DDC AND ITS INTERSECTION WITH
PROGRESSIVE OUTFLOW BOUNDARY INITIALLY OVER RAWLINS COUNTY.  LEADING
SUPERCELL OVER SERN PORTIONS WW...ENE OF GLD...HAS EVOLVED INTO
QUASI-LINEAR CONVECTIVE SEGMENT...WITH EXTENT OF ITS SEWD PROGRESS
STILL UNCERTAIN ATTM GIVEN MIXED SIGNALS IN PARAMETER SPACE.  LIFT
INVOF THESE BOUNDARIES MAY HELP TO FOCUS THIS ACTIVITY AND/OR
SUPPORT NEW DEVELOPMENT ALONG OUTFLOW EXTENDING TO ITS W.
HOWEVER...MODIFIED RUC SOUNDINGS INDICATE PROGRESSIVELY STRONGER
MLCINH WITH SEWD EXTENT ACROSS KS...WHICH ONLY WILL STRENGTHEN THIS
EVENING WITH ONSET OF SFC DIABATIC COOLING.  PRIND UPSCALE COLD-POOL
ORGANIZATION AND RELATED FORCED ASCENT WILL BE NEEDED TO COUNTERACT
THAT TENDENCY FOR ACTIVITY TO LAST MORE THAN A FEW COUNTIES PAST
EXISTING WW BOUNDS.  IF CONVECTION CAN SURVIVE ADVERSE ENVIRONMENTAL
INFLUENCE FOR ANOTHER COUPLE HOURS...DVLPG LLJ WILL AID IN POTENTIAL
NOCTURNAL ORGANIZATION.  ACTIVITY N OF OUTFLOW BOUNDARY OVER SWRN
NEB AND NWRN KS MAY POSE THREAT FOR HAIL AND ISOLATED DAMAGING
GUSTS...THOUGH WIND POTENTIAL WILL BE CONSTRAINED BY STATIC
STABILITY IN RELATIVELY FRESH OUTFLOW LAYER.  TSTMS ALSO MAY FORM
FROM TOWERS ALREADY EVIDENT OVER NRN PORTION OF FRONT
RANGE...ESPECIALLY WITH AIDED LIFT FROM OUTFLOW...AND MOVE EWD-SEWD 
WITH POTENTIAL FOR ISOLATED SVR.

ELSEWHERE...WIDELY SCATTERED STG-SVR TSTMS MAY CONTINUE TO DEVELOP
OVER HIGHER TERRAIN OF ERN WY AND MOVE EWD TO SEWD ACROSS ADJOINING
PLAINS...INCLUDING ACTIVITY ALREADY OBSERVED BETWEEN GCC-CDR MOVING
TOWARD EXTREME SWRN SD. NARROW CORRIDOR OF FAVORABLE MLCAPE AND
RELATIVELY WEAK CINH IS EVIDENT NEAR AND W OF 104W AMIDST 50-60 KT
EFFECTIVE SHEAR.  FARTHER E ACROSS SRN SD AND NRN NEB...LOW-LEVEL
THETAE DIMINISHES STEADILY...WITH ENELY LOW-LEVEL FLOW CONTRIBUTING
TO NEGATIVE THETAE ADVECTION AND REINFORCEMENT OF STRONGER CINH.

..EDWARDS.. 08/09/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ICT...GID...LBF...DDC...UNR...GLD...BOU...CYS...
RIW...

LAT...LON   40060505 42390529 43200633 43640640 43770478 43230282
            42080247 41180102 39339911 37929858 37980063 39200164
            40060505

Mesoscale Discussions in Kansas, 2011Mesoscale Discussions in Nebraska, 2011Mesoscale Discussions in Colorado, 2011Every mesoscale discussion in 2011

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.